1. Field of the Invention
The present invention relates to a lens barrel, and in particular, relates to a cam ring provided in a lens barrel.
2. Description of the Related Art
In a known lens barrel used in a camera, a single drive ring (cam ring) which is rotated to move a plurality of movable members (in general, lens groups) in an optical axial direction is provided with a plurality of cam projections.
However, if the cam ring has a plurality of cam projections, in case where the cam projections overlap each other in the optical axis direction, it is difficult to mold the cam ring because two molding dies for forming the cam ring should be pulled away from each other in the optical axis direction while being rotated respectively in a direction opposite to each other.
The present invention provides a lens barrel having a cam ring which can be easily molded.
For example, a cam ring is rotatable about an optical axis, and at least two linearly movable members provided inside the cam ring, the linearly movable members being linearly guided in an optical axis direction. A plurality of cams are formed on an inner peripheral surface or an outer peripheral surface of said cam ring, at least one pair of the cams overlap each other partly or completely as viewed in the optical axis direction, one of the pair of cams is a cam projection and another of the pair of cams is a cam groove, and a follower recess portion and a follower projection portion, which are relatively movably fitted into the cam projection and the cam groove, respectively, are respectively formed on the linearly movable members.
The lens barrel can include a linear movement guide cylinder provided inside the cam ring, the linear movement guide cylinder having at least two linear movement guide grooves extending parallel to the optical axis. At least two radial projections are fitted into corresponding the linear movement guide grooves, wherein the follower projection portion and the follower recess portion are respectively formed on the radial projections.
The cam projection and the cam groove can be linear. Alternatively, the cam projection can be a non-linear cam and the cam groove can be a linear cam.
The linearly movable members can include a first moving frame and a second moving frame, wherein the follower projection portion is formed on the first moving frame, and wherein the follower recess portion is formed on the second moving frame.
According to another embodiment, a lens barrel is provided, including a cam ring which is rotatable about an optical axis, and at least two linearly movable members provided in the cam ring, the linearly movable members being linearly guided in an optical axis direction. The cam ring includes a cam projection and a cam groove, each having a circumferential component and an axial component, formed on an inner peripheral surface of the drive ring. The linearly movable members respectively include a follower recess portion and a follower projection portion, which are relatively movably fitted into the cam projection and the cam groove, respectively.
According to another embodiment, a cam ring of a lens barrel is provided, including a cam projection and a cam groove on an inner peripheral surface of the cam ring, the cam projection and the cam groove having a circumferential component and an axial component. A follower recess portion and a follower projection portion, which are respectively formed on linearly movable members provided inside the cam ring and are linearly guided in an optical axis direction, are relatively movably fitted into the cam projection and the cam groove, respectively.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-335435 (filed on Oct. 31, 2001) which is expressly incorporated herein by reference in its entirety.